Amber had swollen glands and frequent headaches, and felt surprisingly weak. She was so tired that she had trouble concentrating at school and her grades began to drop. Some days, she found it hard to get out of bed.

Amber had been feeling like this since August — and it was now March. Her parents thought she might have mono, so they took her to the doctor. But after a physical exam and several blood tests, Amber's doctor said she had chronic fatigue syndrome.

What Is Chronic Fatigue Syndrome?

Chronic fatigue syndrome (CFS) is a complicated disease for doctors to diagnose — and even fully understand. Although it is a physical condition, CFS also has psychological components. This means that someone with CFS may feel physical symptoms, such as headaches or joint pain. But the person may also notice emotional components to the illness, such as a loss of interest in favorite activities.

To make it even more complicated, different people with CFS can have different symptoms. And the symptoms of CFS often mimic those of other health conditions, like mono, Lyme disease, or depression. As if that's not hard enough, symptoms of CFS can vary over time, even in the same individual.

All of this makes treating the illness a little more complicated because no single medication or treatment can address all the possible symptoms.

What Causes It?

Scientists have researched CFS for more than 20 years, but they still don't know for sure what causes it.

Many doctors now believe that the way certain conditions interact within the body and mind might leave some people at risk of developing the condition. For example, if someone has a virus and is under a lot of stress, the combination of these two things might make the person more likely to develop CFS.

Doctors currently believe that the following things might interact with each other in this way, putting certain people at risk for CFS:

Infections. Experts have wondered if infections like measles or Epstein-Barr virus (the virus that causes mono) might increase the risk for CFS. The role Epstein-Barr plays in CFS is still debatable, since studies have failed to confirm it as a cause.

Problems with the immune system, such as allergies.

Emotional stress. Scientists have found that people with CFS sometimes produce fewer stress hormones like cortisol, and this could affect the immune system.

Researchers also have discovered that some people with CFS have a type of low blood pressure and are looking into whether there's a connection between this and CFS.

Who Gets CFS?

Chronic fatigue syndrome can affect people of all ages and ethnicities, although more girls than guys get CFS. CFS is very rare in kids. A few teens do get CFS, but it's more likely to happen to people in their forties or fifties. Teens with CFS seem to improve over time much more frequently than do older patients.

Sometimes different people in the same family get CFS. This may be because the tendency to develop CFS is genetic. Doctors are also pretty sure the disease is not contagious.

How Do People Know they Have CFS?

Right now, there's no test to tell if someone has CFS. Because the illness can be hard to diagnose, the Centers for Disease Control and Prevention (CDC) established two criteria to guide doctors in knowing when a patient might have chronic fatigue syndrome:

Unexplained fatigue that lasts for 6 months or longer. Someone with CFS feels overwhelming tiredness and lack of energy that can go on for months with no obvious cause. This kind of fatigue makes it really difficult to get out of bed, get dressed, and eat. It impacts school, work, and anything a person does for pleasure — even just going to the movies or playing an instrument. CFS fatigue does not get better with rest or sleep.

Four or more of the following symptoms:

difficulty with short-term memory or concentration

sore throat

tender lymph nodes (glands)

muscle pain

joint pain without swelling or redness

headaches that are more severe or different from usual headaches

sleep that doesn't help a person feel rested

tiredness or exhaustion that lasts more than 24 hours after an athletic event

To be diagnosed with CFS, a person must have both the long-lasting fatigue and four or more symptoms from the list above.

What Do Doctors Do?

A doctor will take a detailed medical history and perform a thorough physical exam, usually along with a number of lab tests, in order to rule out the following:

any medical condition that may result in extreme fatigue, such as hypothyroidism (low levels of thyroid hormones), lupus, sleep apnea, or obesity

medications or use of any drug that may be causing fatigue

previous or current conditions such as depression, an eating disorder, psychiatric illness. To better understand these conditions, a doctor may request that a person meet with a psychologist or a therapist who can help determine how they might be affecting the person and if they're contributing to or masking CFS.

After ruling out these conditions, doctors will often suggest that a patient meet with a therapist before diagnosing CFS. Why? Because it's important to have as much information as possible about how the symptoms affect a person's overall mental health, including memory, personality, ability to concentrate, and overall outlook on life.

How Is CFS Treated?

There's no known cure for CFS. Although there is no hard and fast treatment, experts say that these lifestyle changes can help:

Include regular, carefully planned exercise in your daily routine. Exercise can provide healing movement, increased energy, and feelings of well-being. People with CFS should pace themselves while doing any physical activity that requires exertion. Everyone's level of tolerance is different. In 1999, soccer star Michelle Akers, who has CFS, played most of the World Cup championship game before having to give in to exhaustion in the final 15 minutes. But for a few people, the disease is so severe that exercise can mean doing a few hand stretches or picking up objects. Explore with a doctor what's right for you — you don't want to overdo it and get discouraged. Several studies confirm that "graded exercise" (which means starting with small activities and slowly working up to a higher level of exercise) is very helpful in CFS recovery. People with CFS are often "out of condition" so getting back into exercise in stages helps.

Follow stress-management and stress-reduction techniques. A doctor or therapist can teach these techniques — they're great strategies for taking control of certain aspects of the illness.

Eat a healthy diet. Though there is no scientific evidence that poor nutrition plays a role in CFS, eating well may help minimize symptoms and general discomfort. Doctors agree that people with CFS should avoid heavy meals, alcohol, caffeine, and large quantities of junk food. Some people find that a registered dietitian (RD) or nutritionist can suggest menu plans to help reduce symptoms of fatigue.

Think "alternative." Acupuncture, reiki, massage, stretching, yoga, and t'ai chi seem to help many people with CFS — but it's a good idea to keep your doctor informed about any other treatments you're trying.

Counseling and Medications

In addition to lifestyle changes, meeting regularly with a licensed therapist or counselor can help in CFS treatment. (So can getting involved in a support group for people with CFS.) The main goals of therapy are to help people cope with the illness and to change negative or unrealistic thoughts or feelings into positive, realistic ones. Having a positive feeling that you can get better is very helpful to CFS patients.

Some people find that antidepressant medications, taken under a doctor's supervision, can help ease the symptoms of CFS. And prescription or over-the-counter pain medications and anti-inflammatory drugs (such as ibuprofen) may also help some people.

Because scientists have not found any link between viruses or other types of infections and CFS, doctors don't treat the illness with antibiotics or antiviral medications. (Doctors have tried using these medications with CFS patients in the past, but they have not helped.)

Coping With CFS

Therapy and support groups can help teens with CFS and their parents deal with the academic or social challenges brought on by the illness, such as missed school, falling grades, or withdrawal from friends and social situations.

Here are some other ways to cope:

Recognize and express your feelings. Strong emotions are a part of the illness. Feelings like sadness, anger, and frustration are completely normal — and acknowledging how you feel and recognizing that it's not your fault are important coping mechanisms. Recognizing emotions (rather than suppressing them or pretending you're OK) can help you figure out what's behind your feelings and allow you to address problems.

Write it down. If your memory and concentration are affected by chronic fatigue, it can help to write things down. For instance, keep lists and make notes to help keep yourself on track. It can also help to keep a daily diary of feelings and energy highs and lows. This diary can be a valuable coping resource, allowing you to share information that might help your doctor. You can also track trends — for example, if your energy is high at a certain time of day and low at another — that will help you figure out when to exercise or do other activities.

Allow more time to do things, especially activities that require concentration or physical exertion. Seek support from family, teachers, and friends.

Get information about CFS from credible sources. There's so much misinformation and confusion about this disease that it's really important to know and trust your sources.

Getting Well

For most people, the symptoms of CFS are most severe in the beginning, and afterward they may come and go. According to the CDC, almost half of all CFS patients experience partial or full recovery within 5 years after the CFS symptoms began — once again, the outlook is better for teens than for adults.

Most important, don't give up. There's no doubt that CFS can be hard, and it's easy to become demoralized. But teens with CFS generally get better faster and recover from CFS more completely than adults do.

Many experts stress that it's more important for people with CFS to keep a positive approach to getting well instead of looking for the reason why they developed CFS. Unfortunately, many people spend too much time looking for a single cause and not beginning therapy — and therapies like the stress-management techniques and graded exercise previously mentioned have been shown to be effective in many cases. In other words, even without knowing the exact cause of CFS, people who take action and approach the condition with a positive outlook can have a good outcome.

CFS might be one of today's most misunderstood illnesses, but awareness is growing and scientists are working to find out more about it every day.